X-RAYS IN PODIATRY
Roentgenology is the science that deals with the use of the Roentgen,
or X-rays, in all their applications. The subject is divided into
three parts, each distinct from the other, and with special required
study for each part. The first branch of roentgenology is known as
_roentgenotherapy_ or _actinotherapy_, and comprehends the treatment of
disease by the use of the X-rays or by other radiant energy.
Roentgenotherapy, to be intelligently applied by the practitioner,
requires a thorough knowledge of pathology and is strictly within
the province of the licensed doctor of medicine. The second branch
variously styled _fluoroscopy_, _skiascopy_, _radioscopy_ or
_roentgenoscopy_, is utilized for examining the various parts of
the body by projecting the X-rays through the body and fixating
the shadows cast on the fluoroscope. This branch of the science of
light is of great assistance in diagnosis and is used extensively in
surgery for the location of foreign bodies in the tissues. The third
division of roentgenology is called _radiography_, _skiagraphy_ or
_roentgenography_, and consists of the making of X-ray photographs by
passing the ray through the body in front of a photographic plate.
This branch is of great importance to the podiatrist because of the
value it possesses in the diagnosis of foot lesions, involving the bony
structures; it often clears up a doubt as to the true state of a lesion
when other means have failed. The soft tissues through which the ray
passes readily appear in light shadow, while the bones, because they
are solid, cast a darker shadow on the plate.
Experiments with electricity and with the modifications of the various
currents of electricity, have been responsible for all of the new
discoveries and inventions along these lines, and the same may be said
of the X-rays.
The two divisions of electric current are the direct and the
alternating, named after the direction in which they flow. The direct
current moves in one direction and may be likened to the flow of water
from a faucet, while the alternating current does not maintain a
steady pressure nor does it flow in the same direction continuously.
The alternating current, which is commonly used for lighting purposes,
reverses its direction of flow and pressure 120 times per second. It is
therefore called 60 cycle current, in that it makes 60 complete cycles
per second. The alternating current may be likened to the tide, which
rises and falls every twelve hours. Instead of passing from ebb to
flood and back again each twelve hours, the alternating current, used
for illuminating purposes, does so in one-sixtieth of a second.
The alternating current, is of most value to the sciences, because its
voltage or pressure may be easily changed. Thus it can be raised or
lowered by passing it through special apparatus. One particular form
of alternating current has a voltage of from 30,000 to 120,000 and can
be used for the production of Roentgen rays, if it be transformed into
a so-called pulsative or unidirectional high tension current. This
transformation is easily brought about by modern Roentgen ray apparatus.
The discovery of the X-rays was preceded by an improvement in the
knowledge of alternating currents. Many scientists were experimenting
and looking for new rays and currents, and after the invention of the
air pump and the production of glass globes, from which the air was
removed by means of the pump, Geissler invented the process of sealing
platinum into glass and produced the Geissler air pump, which is used
to the present day. This made it possible to seal electric conductors
into vacuum tubes.
Following this, Faraday and Maxwell developed the electro-magnetic
theory of light and laid the foundation for a theory of the Roentgen
ray, which, although later considerably changed, has proven one of the
most useful adjuvants to the science of physics. The period between
1840 and the discovery of the X-rays was an active one in electric
experimenting. Many men were interested in this work, and their
observations and discoveries were important in the final discovery of
the rays. In fact, Roentgen’s discovery was fully expected, inasmuch
as several investigators, including Sir William Crookes and Roentgen
himself, were convinced that rays existed of which they knew nothing.
The earlier of the two workers, Crookes, had probably produced X-rays,
but overlooked them and it fell to Roentgen to become aware of the
conditions under which they were produced. He called them X-rays or
unknown rays, but after a time, they were named after him, and are
known in science as Roentgen rays. Roentgen wrote and published three
papers on the subject and these have become classics on this topic. All
of the facts announced by him at that time continue to be accepted,
because, notwithstanding all the work done along these lines, they have
never been disproven.
Experiments have been continuous, and gradually the types of generators
and tubes have changed, always improving. Where at first only simple
work could be accomplished, the most wonderful things in this art are
now being done, with probably many more wonderful things still to
come. The dangers to which the earlier workers were subjected have
been gradually eliminated, and today with proper care, the danger from
the X-rays has been reduced to a minor factor. This danger came about
from lack of knowledge of what occurred in the tube when the ray was
being generated. There are three rays produced, one of which causes
destruction of the human tissues, when exposed for a prolonged period
of time. By preventing the passage of this ray, by the use of lead and
lead glass, as protective mediums, the danger has been practically
controlled.
X-RAY APPARATUS
The apparatus used in the generation of the X-rays consists of a
generator, a vacuum tube and an appliance for holding the tube in a
fixed position, called the tube stand.
=The Generator.= The generators used in X-ray work are of three types,
the motor generator, the interrupterless type and the coil generator
with a chemical interrupter.
The function of the Roentgen ray apparatus is to produce high potential
electric discharges in one and the same direction, or what is known
as a unidirectional current. Dependent upon the kind of current used
to start with, distinction can be made between the types of apparatus
previously mentioned. These types are operated by either direct or
alternating current.
Direct current apparatus requires an interrupting device for the
purpose of producing the necessary change of flux of magnetic lines in
the inductive part of the apparatus. Interrupting devices, which are
used in connection with such apparatus, are of three kinds: _first_,
the hammer interrupter; _second_, the mercury interrupter; _third_, the
electrolytic interrupter. The function of any one of these interrupters
is to break up the continuous flow of direct current into small
fragments. Each one of these fragments then produces one impulse of
high potentiality, which is then directed through the tube.
The alternating current, as its name implies, is already interrupted,
but the impulses are alternately changing direction, passing first
in one direction and then in the opposite direction. Hence, if the
alternating current is used as a primary source of electric energy,
then the secondary or high potential impulses will also be changing
their direction alternately. Two methods are used in employing the
alternating current as a primary source of energy. The first consists
of the suppression of one phase (that which would pass in the negative
direction) by means of the so-called rectifier cell. The second
consists of producing high potential impulses which flow in alternate
directions, and to then redirect these impulses so that all of those
passing through the tube are in the one and the same direction.
[Illustration: INTERRUPTERLESS TYPE GENERATOR]
Accordingly, X-ray apparatus can be divided into the three classes
previously mentioned. The coil, consisting of an induction coil
activated by direct current, which is broken into small sections by
the interrupter; or the induction coil which is energized by the
alternating current of which one phase is suppressed through a liquid
rectifier cell, and in which the proper interruptions are again
produced by some interrupting device. The most extensively used type
of apparatus is known as the “interrupterless machine.” This machine
operates on either the direct or the alternating current, but, if
the direct current is used as a primary source, it is transformed
into an alternating current by means of a rotary converter or motor
generator set. The alternating current, therefore, either produced or
already available, passes into the primary coil of a transformer which
changes it into alternating impulses of high potentiality. In order
to transform them into impulses, all of which shall pass in the same
direction, a so-called rectifying system is employed. This consists
of either a disk or of cross-sticks, which are so arranged that they
produce contact with both terminals of the transformer in such a way
that current of the same polarity, the unidirectional current, is
always delivered to the tube. The name “interrupterless machine” merely
implies that the devices used for interrupting the primary current have
been eliminated.
There is one other type of apparatus which is built on the principle of
an electrically oscillating system. Here again a start is made with the
alternating current, obtained either from the line or by changing the
direct current by means of an interrupter. The current is transformed
through a so-called step-up transformer into one of high potentiality
which is then still alternating. This current oscillates over a spark
gap. Parallel to this spark gap a resonator is connected in which
impulses are produced that correspond to the discharges over the gap
and which, if applied to a specially built, so-called high frequency
Roentgen ray tube, will produce X-rays. Since the principle of electric
oscillations of a high frequency is used in this type of apparatus, it
is generally called the high frequency Roentgen ray apparatus.
[Illustration: TUNGSTEN TARGET TUBE]
=Roentgen Ray Tubes.= The various types of apparatus previously
described require special forms of Roentgen ray tubes. For the coils
by virtue of their relatively small capacity, platinum target tubes
are generally employed. The capacity of the interrupterless type being
considerably higher, the use of a material of greater resistance as
a target is necessitated. For this purpose tungsten is generally
employed. For the high frequency, or Tesla coils, a tube which embodies
a rectifying or valve action device is necessary.
The mechanism of the production of Roentgen rays can be described
in the following way: the cathode, or negative terminal of the
tube, consists of a hollow spherical surface of aluminum. When this
electrode is attached to a negative potential, a stream of negative
ions or cathode rays is projected perpendicular to the surface of
the electrode. By reason of its curvature, the electrode is therefore
focused to produce a converging beam of cathode rays, the area of which
is smallest where, in the centre of the tube, the tungsten block or
anticathode is placed.
According to whether the area selected for the location of the
anticathode is small or large, the possibility to distinguish between
fine, medium or broad focused tubes arises. The discharge from the
negative electrode takes place, dependent upon conditions which give
to the discharge either a high or a low velocity. If the velocity is
high, the change from kinetic energy to Roentgen ray energy will be
greater than if the velocity of the cathode ray stream is decreased.
In the latter case, the radiations will have less penetrating power.
The velocity of the discharge must therefore depend upon the magnitude
of the charge on the negative electrode, and also upon the number of
gas particles present in the tube at that time. If there is a large
quantity of gas present, there will be a reduction in the speed of the
ray, due to collision and impact with the gas. The penetration of the
Roentgen rays depends therefore directly upon the potential produced
by the apparatus and inversely on the gas pressure (or directly on the
vacuum) of the tube.
For the purpose of controlling the state of vacuum in the tube, a
regulating system has been improvised which, when an electric current
is passed through it, liberates a certain amount of gas which passes
into the tube proper. This is a convenient device for reducing the
vacuum of the tube. Up to the present time, no one has succeeded in
inventing an efficient method or device for removing gas from the tube,
or a means which would help to increase the vacuum. It is for that
reason that operators should guard against reducing the tube unduly.
It is a simple matter to reduce the vacuum but difficult to increase
it. When a tube becomes low (when the gas content is high), resting the
tube by allowing it to remain in its bracket for a period of time,
will usually suffice to increase the vacuum.
The proper care of the tube is essential for good radiograms. It should
be kept free from dust, and before being used the degree of vacuum
should be determined by the testing apparatus on the generator. If
the tube is dusty or dirty, the passage of the rays through the glass
will be hampered, as these particles tend to deflect the rays from
their straight course. If the vacuum of the tube is too high, it will
affect the quality of the plate, and if it is too low there will be no
penetration and therefore a blank plate.
[Illustration: TUBE STAND]
=The Tube Stand.= The tubes used in Roentgenology are delicate
structures and great care must be exercised so as to prevent breakage.
To guard against such damage it is necessary to securely hold the tube
in a proper device while it is being used. The tube stand should be
so arranged that it is possible to raise or lower the tube, with its
connections, without being compelled to touch the tube itself, to swing
it from side to side, to tilt it forward or backward, or in or out.
This is best accomplished by the modern tube stand which is so arranged
that after having set the tube in its proper place, it is no longer
necessary to touch the apparatus in order to secure all of the above
named motions. A careful study of the accompanying photograph will make
this clear.
=The Roentgen or X-rays.= The rays generated in the apparatus
heretofore described, and named after their discoverer, are of a
peculiar character, and although they have proven a boon to mankind,
serious trouble and even death has come to those who in their ignorance
used the X-rays promiscuously. It has been discovered that there are
three distinct rays generated when the high potential current is passed
through the vacuum tube and they have been named after the first three
letters of the Greek alphabet, namely: the alpha, the beta and the
gamma rays. The _alpha_ ray is the ray that is seen in the tube and is
of no consequence. The _beta_ and _gamma_ rays are invisible and it is
these rays that penetrate the tissues of the body. To the gamma ray
is attributed the harmful effects of Roentgen’s discovery. Although
the X-ray is used as a therapeutic measure it should only be applied
by those who have a thorough knowledge of its properties. Prolonged
exposure will cause severe burns, and in some cases continued contact
with the ray has caused cancer. Their action in this respect is due
to the actinic quality of the gamma rays. The symptoms of a burn do
not manifest themselves until a minimum of a week or ten days after
exposure and, when they do appear, they are usually severe. Sloughing
of the tissues takes place, and the wounds produced do not heal readily
and, in consequence, ugly disfiguring scars remain.
=Radiography.= This branch of Roentgenology is of most interest to the
podiatrist. By means of photographic plates, properly exposed and well
developed, it is often possible to make diagnoses where other means
have failed. It is essential for one who would be correct in diagnosing
X-ray plates, to have a thorough knowledge of the structure of the
bones of the foot and to understand the meaning of the various shadows
cast upon the plate.
When the X-rays penetrate the foot they pass through the tissues, and
when they strike a tissue of great density they cannot penetrate it
as readily as the rays passing through a tissue of less density. The
result is that as the rays pass through the foot they cast a series of
shadows on the sensitized photographic plate beneath, the density of
which depends upon the tissues through which the rays have passed. So,
in reality, the plate when finished is not a photograph, as most laymen
imagine, but a shadowgraph or, as it is variously termed, a radiogram
or skiagram.
For the purposes of producing radiographs that are clear and easily
interpreted, it is necessary to have good materials and to follow
the technic of developing and fixing the plate in every detail. The
photographic plates used in general photography do not, as a rule,
give satisfactory results. Plates, with specially prepared emulsions
that are adapted for radiography, are preferred. These plates are
sensitized with a gelatinous substance containing bromide of silver.
When this substance is exposed to the action of the rays it undergoes
chemical decomposition, the degree of which varies with the amount of
exposure. It is upon this decomposition of the salt that the art of
photography depends and so, too, the science of radiography. The plate
is then developed.
Developing of a photographic plate consists of making visible the
metallic silver which is produced by the decomposition of the silver
bromide. This is accomplished by the use of a mixture of chemicals
called the developer. The plate is put into a tray about two inches
deep and large enough to allow for its easy removal, and the developing
solution is poured over the emulsion. Gradually the exposed portions of
the negative will appear and developing must continue until every such
exposed part has been brought out in its fullest detail. The unexposed
portions are then dissolved by placing the plate in a solution of
sodium hyposulphite, sometimes called the _fixer_ or the fixing bath.
As its name implies, this solution permanently fixes the exposed
silver, and if the plate were not treated in this manner the entire
mass would become blackened upon exposure to light.
The preparation of radiographic plates is carried on in a room that
is protected from light with the exception of a dull, red glow from a
“ruby lamp” which has no effect upon the plate. The plate is placed
into an envelope made of black paper, and this in turn is placed, flap
down, into a second envelope of red paper. This insures protection
from light rays when the plate is brought out of the dark room. After
exposure, the negative must be taken back to the dark room before it is
removed from the envelope. After it has been developed and fixed it may
be brought into the light with safety.
The length of time required in making exposures varies with the
different types of apparatus. When the flow of rays is great, it will
require a proportionately shorter exposure. So, too, the length of
exposure with a certain type of generator varies with the part being
exposed. The bones of the fingers would require less time than those
of the leg, while the bones of the head would require more time than
either of the above for the production of a clear radiograph. It is
essential in all branches of radiography to remember that the part to
be skiagraphed be parallel to and in close proximity to the plate. This
will prevent elongations and foreshortenings of the shadows cast.
[Illustration: SPUR ON THE UNDER SURFACE OF THE HEEL]
DIAGNOSIS OF RADIOGRAPHS
There are several lesions of the foot commonly arising in the practice
of the podiatrist, which are easily recognized by radiographic
examination but which otherwise are difficult of diagnosis. Some of
these cases are shown in the accompanying pictures, which were selected
from a large collection at The First Institute of Podiatry of New
York City. They are characteristic of the lesions they depict, and
it is needless to emphasize their value as an aid to diagnosis. If a
condition involves the bony structure of the foot, clinical symptoms
are never so certain that an absolutely positive diagnosis can be made,
but the X-ray plate readily reveals such disturbances so that there is
no doubt left in the minds of the practitioner as to the exact nature
of the trouble. Periostitis, exostosis, fractures, arthritis, bone
abscesses, bone ulcers, etc., are thus easily distinguished.
=Periostitis.= Periostitis is an inflammation of the periosteum, the
outer covering of the bone. There are two types, the acute and the
chronic, both of which are not really diseases themselves, but are
indications of the reaction of the periosteum to some irritant. In
acute periostitis the X-ray plate shows a slight destruction of the
outer portion of the bone, and a slight thickening of the periosteum,
and if suppuration is present, the lesion is a mild osteomyelitis
rather than a periostitis.
Chronic periostitis causes an increase in the osteogenetic cells of
the periosteum and is common in a great many lesions. Trauma, blows
or contusions cause a chronic thickening of the bone covering with
additional bone formation, as do syphilis and superficial abscesses
in the soft tissues, in the immediate vicinity of long bones. Thus
chronic ulcer of the leg over the shaft of the tibia will produce this
condition. The picture shows that the even line of the bone surface is
lost, and there is a rough, uneven edge, with or without an increase
in the bone cells. The entire shaft of the bone is often thicker than
normal, especially in the metatarsals, and it is quite common to find
one of these bones greatly increased in size. The fourth metatarsal is
the one most usually affected.
=Exostosis.= This lesion is common in the foot, and is a source of
great pain and annoyance. It is usually the result of a chronic
bursitis which has affected the periosteum over a localized area. Due
to the destructive changes brought about by the inflammatory processes,
the periosteum is absorbed and the bone cells beneath protrude in
the form of a spur which shows on the plate. The most common site of
exostosis of the foot is on the inferior surface of the os calcis,
under the calcaneo bursa. The part is somewhat swollen and is extremely
painful when pressure is brought to bear directly over the growth.
The heads of the metatarsal bones on their lateral surfaces are
occasionally affected, especially the outer side of the head of the
first metatarsal. Lateral pressure gives rise to pain in this type of
exostosis. The treatment for all exostoses is purely surgical.
=Fractures.= There are several kinds of fracture, and they are
classified variously, but for the purposes of the podiatrist, the
following types, with the description of each, will prove sufficient:
=Incomplete Fractures=, among which are the greenstick and the fissured
fractures, are those in which there is not a complete separation of the
fragments. The greenstick is really a bending rather than a breaking of
the bone, and is found mostly in children under fifteen and then only
rarely affects the bones of the leg. Fissured fractures are splits or
cracks in the bone which do not separate it into two parts and occur
occasionally in the fibula or in the metatarsals. They are easily seen
in the radiograph by the dark shadow they produce in the region that
would ordinarily appear light. This shadow extends over the entire
length of the break.
=Complete Fractures= are the most common type found in the lower
extremity and are divided according to the line and the seat of the
breach of continuity. Thus we have transverse, longitudinal, oblique
and spiral fractures. The radiograph will reveal the nature of the
break, and a dark shadow will be cast between the fragments of bone.
The most common of these found in the leg are the oblique and the
spiral fractures.
=Comminuted Fractures= are those in which there is extensive
splintering of the bone adjoining the fracture or one of the fragments.
This class of fracture does not occur in the foot.
=Impacted Fractures= are those in which the fragments are driven into
each other, forming a wedge, thus preventing abnormal motion, so common
in other types. This occurs mostly in the neck of the femur.
=Crushing or Compression Fractures= are those in which the bones are
crushed. The spongy portion and the cortical layer are both involved
and in some cases the bones may be pulpified. The tarsal bones are
subject to this type of fractures as the result of falls from heights,
upon the soles of the feet. (See accompanying picture of fracture of
the os calcis.)
=A simple fracture= is one in which a wound of the skin is absent, or
if present, there is no connection between it and the broken bone.
If the bone is broken in two or more places or if two or more
non-adjacent bones are simultaneously broken, the condition is called a
=multiple fracture=.
[Illustration: FRACTURE OF THE OS CALCIS]
=A compound fracture= is one in which the fragments of bone pierce the
soft tissues and protrude beyond the skin.
It is essential in examining a patient who has suffered from a recent
fracture, to obtain a history of the case as well as a description
of the accident. An examination of the part should be made, and the
various symptoms such as deformity, abnormal mobility and crepitus
should be noted. The X-ray picture is then taken and if a fracture is
found, the case should be put in the hands of a competent surgeon for
immediate and proper treatment.
=Sesamoid Bones.= The sesamoid bones which are found in the flexor
tendons under the head of the first metatarsal bones, are subjected to
injury in those who follow vocations in which the ball of the foot is
put to great strains. Among such may be mentioned dancers and acrobats.
The normal position of these bones is directly beneath the head of the
first metatarsal bone, and when this part is put to a great strain, the
bones may become fractured, or they may become displaced. The outer
sesamoid is usually forced outward and the X-ray picture shows it in
the first interosseous space. The inner sesamoid is not affected, but
may also be forced outward, and is then found under the outer side of
the first metatarsal, in the normal position of the outer sesamoid bone.
Fracture of these bones is not unusual and is a result of a severe
injury. The line of division is shown by a dark shadow, much the same
as in other fractures. One or both of the bones may be involved. It is
essential to remember that if the bone is broken, the opposite sides
will fit into each other perfectly, whereas, in cases of a freakish
nature, in which there are four sesamoid bones, this will not be the
case.
=Arthritis.= Arthritis, or inflammation of the joints, may involve
any one or all of the structures which make up joints, viz., bone,
cartilage, ligaments, synovial membrane and fibro-cartilage. The acute
forms of inflammation are not detected by the radiogram, but the
chronic type leaves its characteristic marks which, when present,
are easily seen. The synovial covering of the ends of the bones
is destroyed, and shows a rough, uneven surface. In cases of long
standing, there is complete bony ankylosis, and the shadows of the
joint line are completely obliterated. This is particularly true in the
tarsal joints, in which the joint lines between the bones can hardly be
seen. There is no motion in such joints, and in milder cases, in which
no union has occurred, the sensation of crepitus is conveyed to the
hand if the joints are moved passively. Tubercular arthritis shows a
rarification of the bone with a thickening of the periosteum.
=Arteriosclerosis=, or hardening of the arteries, is often detected
by means of the X-ray picture. Light shadows cast in the normal dark
shade produced by the soft tissues, which appear over the course of the
arteries, are indications of this condition.
This disease of the arteries causes a change in the vessels whereby
there are calcareous salts deposited in the middle coat. These salts,
containing the metal calcium, are not readily penetrated by the ray,
and thus a difference between the artery and other soft tissues is
established.
There are many other conditions in which the X-rays are a valuable aid
in making diagnosis, but these are of no interest to the podiatrist,
being within the exclusive province of the physician and surgeon.
The reader is referred to books which deal with the subject of
Roentgenology exclusively, for further information upon the subject.
[Illustration: HALLUX VALGUS]